What plant is that?

Click on photo below to view larger image

Ditch Stonecrop
Ditch Stonecrop flowers Ditch Stonecrop fruit
Top and lower right photos: © Francis R. Underwood 2020
Lower left photo: © 2008 Katy Chayka, via Minnesota Wildflowers,
https://www.minnesotawildflowers.inf

The mystery plant for October is listed as rare in RI.  This plant can be found in wet or muddy habitats.  It grows from 2” to 30” tall.  It is a perennial with rhizomes. The leaves are alternate and toothed.  The flowers have 5 sepals (usually no petals) and 5 carpels. The carpels turn red in the fall. It has been placed in its own family.

It’s. . .

Botanical Name:
 
Penthorum sedoides 
Common Name:
  Ditch Stonecrop
Family:
  Penthoraceae (Ditch-stonecrop family)
Habitat:
  Muddy wet areas